If you want to get out into the water on your own, you’ll find plenty of places to kick off from shore. The most popular spot is the Avalon Underwater Park (Casino Point). This protected area at the north end of town has buoys and markers to help you find your way around the reefs and keep safe. Not only will you see the famous bright-orange garibaldi fish, you’ll get the opportunity to meet jellyfish, anemones, spiny lobsters, and plenty of other sealife.
Out at the deeper edge of the park, nearly half a dozen wrecked ships await your examination. Snorkeling and scuba tours groups come here, as do locals and visitors who rent equipment from local shops and shacks or bring their own. Expect big crowds on summer weekends.
If you prefer to take a guided tour, a number of companies offer snorkeling, scuba, kayaking, and combinations all around the island. Catalina Snorkel & Scuba (877/766-7535, www.divecatalina.com ) offers guided snorkel tours of the Lover’s Cove Marine Reserve that include all equipment with the fees. This clear-water preserve sits just southeast of the boat terminal, and includes a life-filled kelp forest. If you’re a certified scuba diver, you can book a two-hour guided tour of Avalon Underwater Park. If you want to become a scuba diver, Catalina Snorkel & Scuba offers certification classes as well as intro tours that give you a taste of the world underwater. Catalina Snorkel & Scuba also offers equipment rental for snorkelers and divers who want to take off on their own.
Another company to try is Snorkel Catalina (877/218-9156, www.snorkelingcatalina.com ). This company specializes in deeper water excursions farther away from shore, taking guests out on a custom pontoon boat all year long. If your purpose in coming to Catalina  is to swim with the dolphins, Snorkel Catalina can make it happen for you. Standard tours run 2–4 hours, and let you check out the prettiest fish, sleekest seals, and friendliest dolphins around the island.
If it’s hardcore scuba you’re interested in, take a walk out onto the Avalon pier to Catalina Divers Supply (800/353-0330, www.catalinadiverssupply.com ). The little blue shack out toward the end of the pier offers everything from certification and referral classes to guided shore dives at the Avalon Marine Preserves to charter trips on the 46-foot Scuba Cat. You’ll see things that just aren’t visible from the surface with a snorkel. The company highly recommends making reservations for any of their tours and trips.